Effects of Landuse Change on CH4 Soil-Atmospheric Exchange in Alpine Meadow on the Tibetan Plateau

Abstract

Degradation of shrub meadows and reclamation of alpine meadows may heavily affect the soil sink for atmospheric methane (CH4), but this is poorly understood. Therefore, in situ measurements of atmospheric CH4 consumption were conducted in four landuse types: natural alpine meadow (NM), Elymus nutans pasture (EP), herbaceous meadow in shrub (HS), and a P. fruticosa shrub meadow (PS) within two years. CH4 fluxes were measured using static chambers and gas chromatography. All four types of land use showed atmospheric CH4 sink throughout the two years, with mean soil CH4 consumption rates at 24.6+/-10.9, 33.8+/-15.0, 39.8+/-10.3, and 28.1+/-12.1 mu g CH4.m(-2).hr(-1) for NM, EP, PS, and HS, respectively. Soil CH4 consumption increased by 40% by reclamation from NM to EP, while it decreased by 30% by degradation from PS to HS. Soil CH4 consumption in four types of land use was significantly correlated with temperature at 5 cm depth (P<0.01) and the soil water-filled pore space (WFPS) (P<0.05). Temperature showed stronger effects on soil CH4 consumption than WFPS, except in NM. UV radiation was positively correlated with soil CH4 consumption with increasing temperature and decreasing soil moisture. These findings indicate that a decrease in the grazing pressure in shrub meadows and increase in the area of artificial pasture reclaimed from alpine meadows would enhance the CH4 sink in alpine meadows on the Tibetan Plateau.